I propose an integrated approach to investigations of issues connected with long-term ambulatory ECG monitoring. I envisage my research culminating in the development of microprocessor-based ambulatory and intra-cardiac arrhythmia monitors. Signal processing: I plan to carry out frequency and time domain analysis of ECG and noise signals. I will identify optimal QRS filter and detector parameters, and signal processors for high resolution ECG. ECG interpretation: I propose a significant-point extraction algorithm that carries out data reduction and pattern recognition. This technique promises to help identify P and T-waves, and S-T segments. Also, R-R and P-R interval predictors will aid in arrhythmia analysis. Electrode studies; I propose experiments on new electrode designs-including a guard-ring ECG electrode, optimal placement, study origins of skin potentials and artifacts, and skin preparations to reduce them. Intracardiac ECGs and defibrillation: In connection with pacemaker and defibrillator developments, I plan to characterize intra-cardiac ECG (including ventricular fibrillation- VFIB) signals, develop algorithms, and investigate other sensors for VFIB recognition. For effective defibrillation, I plan to study current distributions in the thorax. Evaluation: I will develop quantitative measures of performance of arrhythmia detectors (analysis of contingency table, detection curves, utility theoretic analysis, etc.). For evaluation of arrhythmia systems, studies with annotated database, volunteers, and patients are proposed. Long term goals: I hope to design patient monitors utilizing microprocessor and VLSI (very large scale integration) technologies. This research should benefit the development of Holter event-recorders, pacemakers and defibrillators with ECG interpretation capabilities, long-term monitoring and (when necessary) resuscitation of critically ill cardiac patients in their homes. Through the use of intelligent ambulatory and implantable monitors I hope to develop solutions to identification and prevention sudden death in ambulatory population.